It is well known that indigenous, non-pathogenic bacteria predominate on intestinal, vaginal and uro-epithelial cells and associated mucus in the healthy state, and that pathogenic organisms (such as bacteria, yeast, chlamydia, viruses) predominate in the stages leading to and during infections. Organisms such as Escherichia coli, enterococci, candida, Gardnerella and Klebsiella originate from the bowel, colonize the perineum, vagina, urethra and can infect the bladder and vagina. Treatment with antimicrobial agents is required to eradicate the organisms. However, infections can and do recur, for the urinary tract in an estimated 80% of cases. Prolonged use of antimicrobial agents creates drug resistant pathogens, breakthrough infections and a disruption of the normal flora. The possibility that indigenous bacteria have a role in preventing infection has been postulated for many years, but few studies have been carried out to identify specific bacteria and their properties required for such an effect. U.S. Pat. No. 4,314,995 to Hata et al. investigated anaerobic, lactobacilli-like organisms as a means of treating a number of infectious diseases, but no consideration was given to the combined importance of their hydrophobicity, hydrophillicity, adhesiveness to biomaterials, epithelial cells, mucus and tissues, and no discussion was included to prevent urogenital infections. U.S. Pat. No. 4,347,240 to Mutai et al. discloses a composition and method employing a specific strain of lactobacilli to inhibit tumour growth.
In recent years, our group has investigated the use of lactobacillus to prevent recurrent urinary tract infections, particularly in adult women. Our conclusion has been that the ability of lactobacilli to adhere, inhibit, competitively exclude and coaggregate formed the basis for the protection of the host. However, new and more important information has now come to light, further to human and experimental studies. The invention now takes into account a new infectious state (post-antimicrobial urogenital infections) as distinct from simple urinary tract infection. The former is initiated following use of antimicrobial agents. This application was not obvious previously, as previous literature has concentrated on virulence characteristics of pathogens causing problems, ignoring the fact that recurrences can follow the use of external agents. We previously recognized resistance to nonoxynol-9 as being important for selection of lactobacillus. However, the usage of this agent is not universal, and just because a strain can resist its action does not infer that it offers every lactobacillus strain the crucial component of protecting the host.
The ability of lactobacillus to produce inhibitory substances has been believed by us to be important. One obvious such product would be hydrogen peroxide. However, based upon our latest findings, this property is present in strains that do and those that do not protect women from reinfection. Thus, inhibitory activity is not the primary mechanism for prevention of infection.
The adherence of lactobacillus to epithelial cells has been regarded as important in the context of blocking access of pathogens to surfaces. However, what was not recognized previously was the hydrophobic and hydrophillic properties of these strains and the production of proteinaceous adhesions into the environment (supernatant). These new findings were not obvious and in fact describe totally new methods whereby lactobacilli colonize biomaterial and human cell surfaces. The use of intestinal cell monolayers has provided a system more closely related to the in vivo situation, showing that colonization of the intestine (to compete with uropathogenic organisms before they emerge to colonize the urogenital tract and infect the bladder and vagina) must reach higher levels (10 to 165 lactobacillus per cell) to achieve potential protection.
In addition, we now realise that the in vitro adherence levels for lactobacillus to uroepithelial cells bear little resemblance to those found in the in vivo situation, when compared directly. In other words, a count of 65 bacteria per cell in vitro does not always give a count of 65 per cell in vivo. All it can show is that the strain has adhesion potential. In fact, we now know that a level of &gt;0 bacteria per vaginal cell in vivo (along with evidence of some adhesion on cells even when the mean is zero), and a viable count of &gt;100 lactobacillus per ml from a tissue swab, is a preferred characteristic to measure adhesion. The preferred characteristic for the desired result is for a strain to colonize the surface and retain viability and reproduce.
A better understanding of the species of lactobacilli in the vagina has now been acquired by us. In addition, new strains have been examined for various parameters, and their origin, type, identity and properties were not previously known or assumed.
We previously recognized that lactobacillus adhesion to urinary catheters could provide a mechanism for protecting a catheterized patient against urinary tract infection. Infections in these patients are widespread and can be fatal, especially in an acute care setting. Data has been accumulated (Hawthorn and Reid, "Exclusion of uropathogen adhesion to polymer surfaces by Lactobacillus acidophilus", Journal of Biomedical Materials Research, Vol. 24, 39-46 (1990)) to further support the theory that lactobacillus coated onto a catheter can prevent uropathogenic bacteria from adhering. However, the practicality of adhering lactobacillus to a prosthetic device in a manner that would provide a stable product was not obvious, nor was it investigated. Rather, the new information on lactobacillus demonstrates that catheter colonization should come via hydrophobic and hydrophillic adhesion of the organisms to the urethra, from where they themselves will attach to the catheter. This new approach is a significant deviation from the published works, as it takes account of the new lactobacillus properties and the knowledge that catheters are either hydrophobic (TFX silicone) or hydrophillic (Bard and Kendal Foley Lubricated catheters). It also provides a new concept, whereby the lactobacilli do not block uropathogenic adherence as the main means of protecting the host directly, but rather they bind with the uropathogens and form a more normal flora that is less able to infect the host.
The use of skim milk as a potential carrier for lactobacillus was previously considered by us. However, no investigations had been carried out with this substance. In addition, the material was seen as a neutral component that, if anything, would provide a lactobacillus preparation with stability and growth potential in the host. What was not appreciated and what has now been discovered is that specially prepared skim milk and other specific lactobacillus growth factors, called LGF, can be used to stimulate the growth of a patient's own normal flora, to the extent that it could protect the patient against urogenital infection.
By "especially prepared skim milk" is meant skim milk suspended in phosphate buffered saline, autoclaved to eradicate proteinaceous and living contaminants, then freeze dried. By "specific lactobacillus growth factors" is meant substances which stimulate preferentially only growth of lactobacillus and not uropathogens, or alternatively which stimulate significantly more lactobacillus than uropathogen growth. These latter substances are present in skim milk power, lactobacillus microbiological growth media and in other composite compounds and elsewhere.